Aircraft and three-point landing gear for same



0ct. 15, 1935. LSIKORSKY {2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 13 Sheets-Sheet 1 gwuemto'a 190/ aka/09 0a. 15, 1935. 'slKoRsKY 2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 15 Sheets-Sheet 2 Igor 5/jorsky INVENTOR ATTORNEY Oct. 15, 1935. r I. glKQRSKY 2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 13 SheetsSheet 3 BY flZ/ MW ATTORNEYS.

Oct. 1 5, 1935.

l. SIKORSKY AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 13 Sheets-Sheet VENK ATTORNEY k Oct. 15, 193 5. SIKQRSKY 2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 -13 Sheets-Sheet 5 JVVEWTOR.

ATTORNEYS.

Oct. 15, 1935; l. s:KoRsKY 2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 13 Sheets-Sheet 6 If? I H- a p 9' 0 s A 25 2 4 ATTORNEY Oct. 15, 1935. l. SIKORSKY .XIIFICRAF'I' AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 i TO IINSTRUNE NT OILTAN K ATTORNEY l. SIKORSKY 2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME oc't. 15,1935.

l5 Sheets-Sheet 8 Filed April 12, 1929 III l NVEN ATTORNEY Oct. 15, 1935. SIKORSKY AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 l3 Sheets-Sheet 9 ATTORNEY Oct. 15, 1935. SIKORSKY 2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Filed April 12, 1929 13 Sheets-Sheet 10 @or S/ko/my" ATTORNEY Oct. 15, 1935. l. SIKORSKY 2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME 15 Sheet-Sheetll or 572' l NVENTOR v Q k Oct. 15, 1935. 2,017,446

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME l. slKoRsKY Filed April 12, 1929 15 Sheets-Sheet 12 n". an:

ATTORNEY ATTORNEY l. SIKORSKY Filed April 12, 1929 15 Sheets-Sheet l3 Oct. 15, 1935.

AIRCRAFT AND THREE-POINT LANDING GEAR FOR SAME Patented st. 15, 1935 UNITED STATES PATENT OFFiC AIRCRAFT AND THREE-POINT LANDING GEAR FOR S 1 Application April 12, 1929, Seriai No. 354,552

12 Claims.

The present invention relates to landing gear for aircraft, and particularly to landing gear of the three point type. The principal object of the invention is to provide a landing gear of this type so constructed that upon contact with the ground in alighting or in taxiing over the ground, the least possible shock will be transmitted to the aircraft.

With this main object in view, I provide hydraulically cushioned landing means at all three points. Preferably, wheels form the'two forward points and a skid the third point, but it will be understood that skids or the like might be sub I stituted for the Wheels, and that the tail skid may be provided with a drag shoe or with a wheel. Throughout the present specification, I shall refer to landing wheels and a tail skid, but it will be understood that these terms are used merely for the sake of convenience.

The tail skid and wheel supports represent common characteristics, in that each consists of a member directly pivoted at .one end to a structural member of the aircraft, and connected to the aircraft structure at its other end through a'substantially vertically extending spacer. In each instance, the spacer is of telescopic construction-and the telescopic members are collapsible against hydraulic pressure. spacer members thus constitutes a shock absorber. The spacer members for the landing wheels are collapsible or extensible by means of a hydraulic actuating system and thus, in addition to the function of the shock absorber, act as wheel retracting and projecting devices.

The invention not only includes the arrangement of the wheel supports and tail skids relative to the aircraft structure, but also specific structural features of the component mechanisms.

I have used the term faircraft above in its broadest sense, but since the structure to be described and claimed is particularly applicable to aircraft of the land-water-air type. the invention will be described" with reference to an amphibion. f v

The present application is a continuation in part of my copending application Serial No. 314.585, filed October 24, 1928.

In the accompanying drawings,

Fg. l is a front elevation of an amphibion with its landing wheels in operative position.

Fig. 2 is a front elevation of the same showing the landing wheels in inoperative position, and the buoyant members operative.

Fig. 3 isa diagram showing the landing wheel shock absorbing and control mechanism,

Each of the.

Fig. 4 is a plan view of an amphibion in some detail, the arrangement of the wheel supporting mechanism being somewhat difierent from that shown in Figs. 1 and 2.

Fig. 5 is a front elevation of the amphibian 5 of Fig. 4.

Fig. 6 is a side elevation of the same amphibion.

Fig. 7 is an enlarged front elevation of the central portion thereof. I

Fig. 8 is a section on line 8-8 of Fig. 7. 10

Fig. 9 is an enlarged partial side elevation of the amphibian.

Fig. 10 is an enlarged front elevation of the amphibion with parts removed.

Fig. 11 is an enlarged front elevation of the 15 left hand landing wheel and its supporting mechanism with parts in section and parts broken away.

Fig. 12 is a partial plan view of a wheel supporting frame. 20 Figs. 13, 14 and 15 are details of the frame in section.

Fig. 16 shows a detail in face new. Fig. 17 is an enlarged front elevation of the left central portion of the amphibion, partly in 25 section, showing the hydraulic wheel control system.

Fig. 18 is a diagram of the complete system.

Fig. 19 is a plan view of a pressure generating Fig. 20 is a side elevation of the pump of Fig. 19, partly in section.

Fig. 21 is a side elevation of the valve control interposed in the hydraulic system.

Fig. 22 is a front elevation of the same.

Fig. 23 is an axial section through a telescopic wheel supporting member.

Fig. 24 is a side elevation of a tail skid and sup porting means therefor in connection with the stern of the body boat of the amphibion.

Fig. 25 is a section on line 25-25 of Fig. 24.

Fig.26 is a partial elevation taken from the right of Fig. 24.

Fig. 27 is a sectional view of the upper portion of the body boat and of the tail skid supporting mechanism.

Fig. '28 is a longitudinal section through the telescoping members comprised in the tail skid mounting.

Fig. 29 is a plan view of a guide bracket for 59 the telescoping members, one of the latter being shown in cross-section.

Fig. 30 is a section on a longitudinal vertical plane of the rear end of the body boat, the tall skid and its associated cushioning means.

Fig. 31 is a section on line 3l-3l 01 Fig. 30.

Fig. 32 is a rearelevation of a tail skid shoe shown in Figs. 24, 30 and 31.

Fig. 33 is a section on line 33-43 of Fig. 30.

- Fig. 34 is a side elevation of a modified form of tail skid.

Fig. 35 is a longitudinal section of the skid of Fig. 34 and adjacent portion of the body boat.

Fig. 36 is a section on line 3648 of Fig. 34.

Fig. 37 is '1. vertical longitudinal section of the rear portion of the tail skid of Fig. 34.

Fig. 38 is a section on 1ine38-38 of Fig. 37.

Fig. 39 is a plan view of a blank from which the mainbody of the tail skid shoe of Figs. 34 and 37 is formed.

Fig. 40 is a plan view of a cover plate for the tail skid shoe. and

Fig. 41 is a rear view of the shoe partly in section.

Referring first of all to the showings of Figs. 1 to 3, A is the main wing of an amphibion, and positioned therebelow is a body boat B from which lower wings C and D spring laterally and support at their outer ends pontoons E and F. The landing wheels are indicated at G and H, and are supported on axles G and H extending laterally of the body boat and pivoted thereto for swinging movement in vertical planes. Rods G and H are pivoted at their lower ends to the outer ends of axles G and H these rods having at their upper ends piston heads working in cylinders G and H, the latter being pivoted at their upper ends to the main frame structure.

Means are provided whereby hydraulic pressure may be introduced into cylinders G and H above the respective pistons therein, so that rods G and II will be moved to and/or maintained in the position shown in Fig. l with wheels G and H in landing position. Conversely, hydraulic pressure may be introduced into the cylinders below the piston heads so that rods G and H will be drawn inwardly of the cylinders, thereby moving the wheels into the inoperative position shown in Fig. 2, wherein they lie in substantially horizontal planes immediately in advance of the lower wings. As illustrated, axles G and H have their body-attached ends bent upwardly from their wheel supporting portions, which latter, of course, lie in substantially horizontal planes when the wheels are in operative position.

The hydraulic operating medium serves the additional purpose, through means particularly described and claimed in my above mentioned prior application, of shock absorbing means when the machine is landed on the ground .or is taxied thereover. A modified form of cushioning mechanism, still hydraulically controlled, however, will be described hereinafter. i

Fig. 3 shows diagrammatically a hydraulic control system for the wheel retracting and projecting mechanism. According to this figure, K represents a supply tank containing the hydraulic medium, such as oil, glycerine or the like. The

reference character K indicates the outlet line from the tank, while K indicates the return line. A hand pump K ds interposed in line K and when it is actuated liquid may be forced through four-way valve L either through branch M into line M or branch N into line N. If line K is connected into branch M, branch N will be connected through the four-way valve into return line K and liquid will be forced into cylinders' Cland H above the piston heads therein, thereby projecting rods G and H", while liquid in the cylinders at the lower sides of the pistons will be spat see line M and branch M is prevented and the rods 5 are maintained in their projected position. By proper manipulation of valve L, liquid may be forced into the cylinders below the pistons. and an outlet established through line M branch M, valve L and line K Upon thus retracting the rods, the valve ports may again be lapped so that the rods will be maintained in retracted position.

If desired, a power pump can be substituted for hand pump K or added as a second part. The matter to the left of the hand pump in Fig. 3 illustrates a power pump arrangement. At 0 is a power pump driven by a propeller 0 With this wind driven pump, the hand pump is still useful for such operations, as may be required, while the aircraft is at rest, and the hand pump will also be useful in case of failure of the power pump during flight. Being wind driven, the pump will ordinarily be in operation at all times during flight and, consequently, a by -pass 0 controlled by a valve 0 is interposed between intake line 0 and outlet line 0 which are in connection with line K at either side of pump K Valve 0 is normally open so that the operation of pump 0 has no effect ordinarily, except to circulate fluid through the by-pass.

Also connecting the inlet and outlet ports of the power pump is a second by-passO normally closed by the automatic valve 0'', this valve being normally held closed by a spring which permits it to open and thereby provide a direct path from .the outlet to'the inlet port of the power pump should the pressure of the fluid at the outlet of the pump become excessive at any time. A check valve 0 prevents the passage of fluid toward the reservoir. 1

The operation of the device by means of pump 0 is as follows: Valve L having its ports lapped, that,is to say closed, valve 0 will be open and under the influence oi the pump liquid is simply circulated through lines 0* and O and by-pass 45 0". If it is desired to retract the wheels, valve L will be adjusted as above described, and valve 0 closed. Consequently, liquid 'will be fed through line 0 into line K and thence through valve L into line N pump K being of a positive pressure type which will prevent back flow there- ,through.

Valve 0" acts as a safety device to prevent bursting of pipes should valves L and 0 be improperly manipulated. Should pump 0 fail, or should it be out of operation, hand pump K may be used as above described, the non-return valve 0' preventing useless circulation through pump 0.

Figs. 4 to 6 show, as a whole, an amphibion of preferred form. plane and I2 lower planes springing laterally of a body boat I!) disposed beneath the main plane. Outriggers l3 extending rearwardly of the centerplane section of main plane H, support at their outer ends an empennage assembly M, the outriggers, planes and body boat being joined'together by a suitable system of struts. Motors l0 and I0 are suspended below the center section of plane H, and cylinders l9are in pivotal connection with the center section through means supported by the motor supporting frames, as will be hereinafter described. Wheels l5 are supported on axles I! (see also Figs. 7 and 8) and rods l8 are pivoted to the outer ends of axles I1, and at their upper ends are provided with In these figures, l l is amain 60 I porting portions lie in horizontal planes substantially below their points of pivotal attachment to the body boat.

At 29 is indicated a tank containing a supply of the hydraulic medium. Tank is connected by means of the conduit 2i to a pressure gen-- erating device 22 adapted to be actuated by a lever 23. Reference character 25 denotes a supply line leading from the pump 22 to a distribuchairs 38 placed side by side.

tor 24, and 25' denotes a return line leading from the distributor. Lines I9 lead from the distributor to the upper ends of cylinders I9 and lines l9 lead from the distributor to the lower ends of cylinders i9, the distributor comprising valves so arranged as to direct the supply to lines I9 either singly or separately, or to lines I9 either singly or separately so that wheels i5 may be independently controlled. Lines I9 and I9 are lead upwardly through a stream line housing 26 and laterally through branch housings 26.

In the amphibion as illustrated, two motors are provided, these being laterally and symmetrically spaced relative to the body boat. In

'case of failure of one of the motors, an unsymmetrical tractive force is exerted on the amphibion. If the machine is being propelled in the water by only one motor, the distortive effeet may be compensated by lowering'tha wheel beneath the operative motor to a suitablc extent. The increased drag on that side of the boat will relieve the vertical rudder and leave it free and more eifective for steering purposes.

It will be noted from Fig. 8 in particular that the pilots compartment generally indicated by the reference numeral 39, is provided with two Since the control arrangements and devices have been particularly described and claimed in my Patent No. 1,916,444, it will'sufilce here to state that the reference numerals 6i indicate the engine controllevers, 33 indicates levers cooperating with segments 35 to adjust the seats to various heights and retain them in adjusted position, 62 indicates means for controlling the adjustment of the stabilizer and 68 indicates the aileron and elevator control member, which has a pivoted extension 63 so supported that it may be swung to bring wheel ill) in front of either chair 38. r I have described generally above the amphibion structure and the retractible landing wheels and associated devices. I shall now proceed to describe with some particularity the various elements constituting the invention.

I have mentioned that cylinders or tubular members I9 are in pivotal connection with the main plane II through the motor supporting means. The motor supporting frames are particularly shown in Figs. 9, 10 and 17. Since the two frames are identical, it will suflice to describe form tion. The forward ends of these bars are rigidly secured to head ill, and their rearward ends are connected to a block I5. Head 10 has four ears projecting therefrom, the ears being arranged in pairs at each side of the top center of head I0, and to them are secured the lower ends of struts 76, I1, 78 and I9, the top ends of the latter being secured at spaced points to cars secured to and projecting downwardly from the front spar 80 of the main plane. Struts I6 to 19 I are in substantially the form of a W, and their lower ends project forwardly of front spar 80 so that head I0 is positioned somewhat in advance of the latter.

Two struts 8| and 92,'Fig. 10, are secured at 7 their upper ends to the reinforced portion of spar 8D, and their rearwardly projecting lower ends are secured to block 75. Struts 8i and 82 are in substantially V-relation, and their upper ends may be secured to the same ears to which the the front and rear spars.

A plate 85, Figs. 9 and 17, is secured to bars i2 and 73, and has mounted centrally thereof a block 81. A strut 88 is secured at'its upper end to the lower portion of spar 99, and its lower end extends vertically downwardly through a guide aperture formed in block 87. and a registering aperture in plate 86. Strut 98 is thus supported in a fixed position with its lower end positioned in the space between rods ii to 74. The lower end of strut 88 is provided with a knuckle in which is pivotally engaged a flange provided on the top cap of member 89.

Members 88, i8 and i9 constitute in eiiecta linkage system whose members are in substantial alignment when wheel i5 is in operative position. The lower portion of this linkage systhrough a slot 89' of wh'ch member I9 is passed 50 for free oscillation.

In Figs. 11 to 17, I have particularly illustrated the wheel supporting means.

Tubular axle I'I supports at its inner end a knuckle 90 having a shank extending within the axle member, and member I6 supports at one end a substantially similar knuckle 9i and at its other end a knuckle 92. An eye bolt 92' engaged With knuckle 9| is secured to axle I! immediately to the rear of its whecl supporting portion, and likewise secures to the axle a collar 93 having a radial flange 94. Knuckles 90 and 92, are pierced to receive bolts 90 and 92', and they are pivoted to stanchions 95 and 95 which are. secured to the body boat I0, there being a transverse frame member as at 91, Fig. 10, extending between the stanohions at opposite sides of the body boat.

A member I6 joins the inner ends of axle I1 and member I6, the members being secured together by means of clips 98 and 99, an angle bracket 99' bracing members I6 and I1.

Wheel I5 has an internal cup-member IIII with which is adapted to cooperate a brake band mounted on an expansion member I02, which is supported on an annular plate I93 which in turn has its inner margin bolted to the outer margin of flange 94 by means of bolts I03. Collar 93 which supports flange 94, is secured against rotation by bolt 92 and also by keys 93'.

An operating cable I04 is led through an aperture I05 in plate I03, and has its end secured to an operating lever I06 for the expansible member I02. Cable I04 is led to the pilot's compartment through a flexible conduit I01, which has an end nipple I08 secured in a collar I09 surrounding aperture I05.

. Cable I04 and its flexible housing conduit I01 may be lead to the pilot's compartment either through hollow axle I I or it may be trained along the outside of the latter. In either event, the wheels may be moved from operative to inoperatlve position and vice versa without affecting the brake or its operating mechanism.

Cylinder I9, Figs. 11 and 23, is closed at its upper end by means of a cap IIO which, as has heretofore been mentioned, is provided with means for pivotal attachment to the lower end of strut 88. The cap is in threaded engagement with a, sleeve III welded to the upper end of member I9. Member I8 is tubular, and passes into the lower end of cylinder l9 through a plurality of nested sleeves H2, H3 and H4, the latter of which is welded to the lower end of member I9. Reference character H5 and H6 denote packings, the former being compressible when member H2 is screwed'inwardly of member I I3. 9

Member I8 has screwed into its upper end the threaded skirt ofa plug II1, the skirt being terminated upwardly by a radial flange II1 which sets on the upper edge of member I8 and extends therebeyond. Plug II1 has a central upwardly extending hollow stud II 8 screw threaded at its upper end, and disposed on this stud are a downwardly faced packing cup II9, a washer I20, an upwardly faced cup I2I, a; washer or spacer I22, a second upwardly faced cup I23, a spacer I24 anda nut I25 with a locking device I26. A sleeve I21 is interposed between flange II1 of plug H1 and the inner end of sleeve II3. Sleeve I21 is maintained in concentric relation with member .I8 by means of lugs I28 which are in substantial contact with the inner surface of cylinder I9. Sleeve I21 serves to limit the movement of member I8 outwardly of member I9.

Tube I9 communicates with theupper end of cylnder I9 through a connection I29, and tube I9 is in connection with the lower end of the cylinder through a connection I30.

Inwardly of member I8 is a tubular member I3I having screwed into its upper end the externally threaded skirt of a plug I32 having a radial shoulder portion abutting the upper edge of member I 3|. Plug I32 has an upwardly extending stud I38 carrying a downwardly faced packg cup I34, a 'washer I35, an upwardly faced packing cup I36, a washer or spacer I91, a second upwardly faced cup I38 and finally an upwardly castellated nut I39. Member I 3I is provided at its lower end with a spacer ring I 3|.

Projecting inwardly of member I3I is a pin I40 having a radially flanged portion I at its lower extremity. Normally flange I is disposed substantially below the lower extremity ofmember I3I, and the upper end of pin I40 is disposed substant ally a like distance below the upper extremity of an axial bore in the lower portion'of plug I32. Members I40 and I32 are ordinarily yieldingly maintained in this relation by means of a helical spring I42 interposed between the plug and flange or seat I4I.

The lower end of member I8 is closed by means of a cap I43 having an ear I44 pivotally engaged in a knuckle member I45 secured in the outer end of axle I1. A spring I46 of considerably greater strength than spring I42 is interposed 5 between cap I43 and seat MI. The operation of the described arrangement is as follows:

When, for example, the machine is landedon the ground the shock, great or small, has the eifect of moving member I8 inwardly of cylinder 10 I9. This means that there is a tendency for the piston at the end of piston rod I8 to compress the fluid thereabove in cylinder I9. This pressure causes the fluid to pass downwardly through the bore of stud H8 and to impinge against the 15 piston at the upper end of member I3I, causing the latter to move downwardly-against, the force of spring I42. If the landing has been particularly rough, spring I42 will be compressed until the lower extremity of member I3I meets seat 20 MI, whereupon further movement of member I8I is positively transmitted to the relatively strong spring I46. Upon release of the pressure,

springs I42 and I46 again expand, moving the parts to the position shown in Fig. 23, and expelling the liquid from member I8 through hollow stud II8 into the top of the cylinder. It will be understood that fluid introduced into the cylinder through tube I9 will move the main piston and therewith rod I8 downwardly, while liq- 30 uid introduced through tube I9 will move the main piston upwardly, thereby through the intermediary of rod I8 retracting wheel I5.

It will be seen from the above that I have provided a shock absorber adapted first of all to 35 resist relative movement'of its parts through a relative weak compression device, and to resist extreme movement of its parts by a relatively strong compressible device to which force is positively transmitted.

- In Fig. 18, I have shown diagrammatically the hydraulic control system for the landing wheels. As has already been described in connection with Fig. 8, reference character 20 indicates a supply tank for the hydraulic medium, and 2i 2. line 45 leading from the tank to the double action pump 22 and supply line 25, and also in connection with return line 25. Line 25 has two branches each leading-to a four-way valve 24 or 24 With the valves in the position shown in Fig. 18, line 50 25 is in connection with lines I9- and also with instrument board gauges 28 through globe valves 29. Lines I9 are in connection with line 25 through valves 24* and 24'. When cylinders I9 have been filled with liquid, the latter may be 65 retained therein either by check valves 300 and 300 by lapping valves 24 and 24 or by closing 'valves 29. It will be noted, however, that all of these valves are independently operable, so that the hydraulic medium may be supplied to cylinders I9 either singly or together, so that the landing wheels are independently controlled.

As is shown in Figs. 19 and 20, the pressure generating device comprises a pair of aligned cylinders I41 and I48 secured in opposed relation 65 lever 23, liquid is drawn from line 25', and also line 2|, if necessary, and discharged into line 25. Base plate I49 is secured to the floor in the pilot's compartment so as to bring lever 23 within convenient reach of the pilot, as is indicated in Fig. 8.

The relative arrangement of valves 28 and 24 is illustrated in Figs. 2| and 22. According to these figures, the valves are supported on brackets as at I64, which latter are supported on uprights I85 and I66 extending between transverse structural members I61 and I68 of the body boat; Each valve has an operating handle I69 or I18 whose outer ends, Fig. 22, are so bent as to bring them into substantial contact with each other. Lever I69 is provided with a half handle I69 and lever I18 with a half handle I18, the two lying closely together so that while they may be readily grasped simultaneously by the hand of the operator, they may also be operated independently.

Referring to valve 24 the bottom port is in connection with supply line 25, the forward port in connection'with line I9 the rearward port through a connection HI and globe-valve 29 with tube I9 and the'top port is in connection with being applied to lines I9 or whether valves 29 are closed, the gauges will always be in operative connection with-lines 59 so that the pilot may be apprised of the pressure existing therein. Check valves opening when liquid is forced upwardly and closing when liquid is forced downwardly are shown respectively at 388 and 988 It will be remembered that lines I9 lead to cylinders I9 above the piston heads therein.

When levers H99 and I18 are in the position illustrated in full lines in Fig. 21, pressure will be supplied through line 25 to lines I9 and lines I9 will be connected into exhaust lines 25. If levers 599 and I18 are moved to the dotted line position of Fig. 21, line 25 will be placed in connection with lines I 9 and lines I9 will be placed in connection with line 25'.

A tail skid and the supporting means therefor, are shown in Figs. 24 to 33. The stern of body boat I8, is shown in Fig. 24. A pair of angle bars I13 and I14 are disposed along the keel of the body boat at the rear portion thereof, and pro- 'ject somewhat beyond the stern, and are secured to the stern post by means of an angle bracket I15. A pair of plates, one of which is shown at I16, Fig. 24, are secured to the front portions of members I13 and I14, and pivotally support between them'the front end of the tail skid I11.

In Fig. 25, I 18 indicates the keel of the body boat,

I19 the outer sheathing, and I18 the keelson.

The rear end of tail skid I11 has secured thereto by means of bolts I18" and I19 a cast shoe I88 of boat shape as may be most clearly seen in Figs. 31 and 32. The shoe is reinforced by means of longitudinally extending ribs I8I and I82 and a number of transverse ribs, the shoe terminating in a perforated ear I88.

A tubular member I83, closed at its lower end is pivoted between ribs I8I and I82 by means of a bolt I84. The upper portion of member I83 lightness built up of plate material.

passes between the projecting ends of members I13 and I14, and in the bifurcation of a plate I15 secured on the latter. Member I83 has slidable thereon a radially flanged ferrule I85 whose flange rests on the margins of bifurcated plate 5 I15. Clips I86 and I81 which take over the flanged portion of the ferrule prevent its vertical displacement, while permitting its sliding movement in the longitudinal direction of the body boat. Transverse movement is prevented by 10 members I13 and I14. A hollow member I89 fits in member I83 in telescopic relation therewith, and has its lower end closed by a piston head I98 provided with a small axial perforation I98. A gasket I9I is retained on the upper end of mem- 5 her I83 by means of a ring I92. A cap I93 has a shank I94 secured in the upper end of member I89, and an upwardly extending ear I95. Ear I95 is pivotally secured between depending ears I96 of a bracket I91 by means of a bolt I98. A 20 yoke I99 is secured through a central perforation between the lower face of cap I93 and a collar 288 to the upper end of member I89. The yoke carries at its ends downwardly projecting tubular members 28I and 282, which are rigidly secured 5 thereto. At their lower ends, members 28! and 282 are guided in apertures formed in a bracket 283, which is fixed to member I83. Rings 284 and 285 secured to the lower extremities of members 28I and 282 prevent the passage of the latter up- 30 wardiy through the apertures of bracket 283.

Interposed between yoke I99 and bracket 2 83, and surrounding members MI and 282, are a pair of helical springs 286 and 281 which normally hold the parts in the position illustrated in Figs. 35 p 24 and 30.

The telescopic members or at least that portion of member I83, normally below piston I98, is adapted to be filled with a fluid which is retained therein by a plug 288 screwed intothe filling 0 opening.

Landing shocks imparted to the tail skid cause compression of the liquid in the lower end of member I83 between the end wall of the latter and piston I98. This pressure is relieved by the 45 passage of the liquid throughperforation I98, the telescopic movement of parts I 83 and I89 being, however, opposed by springs 288 and 281. The two telescopic members, due to the hydraulic medium contained therein function as a shock 59 absorber, the relative movement of the members being permitting by their pivotal connection with the tail skid shoe and with bracket I91, respectively. Oscillation about bolt I98 is not interfered with by guide plate I15, although the latter pre-' 55 vents lateral distortive movement.

As soon as the load is removed from the tail skid, the telescopic members will be expanded by spring 286 and 281, and the liquid which has been expelled from the lower side of piston I98 will be 5 permitted to return under the force of gravity.

In Figs. 34 to '41, I have illustrated another form of tail skid shoe. The forward-end of tail skid I11 is supported in the same mannerdescribed in connection with Fig. 24. v The shoe, 55 however, instead of being cast, is for the sake of The main body of the shoe is formed from a blank, such as shown in Fig. 39. This blank 289 is provided with lateral cut-outs 2I8-and 2H, and then is bent 70 along the dotted lines to bring the edges of the between the lower portions of the stanchions, and

the lower extremity of member I83 being pivoted between the upper ends of the stanchions by means of a bolt 2| 4. The lower end of member I83 is provided with a filling valve 2I5. Mounted in the shoe to the rear of the stanchions is a mooring member 2l6 in the form of an upwardly projecting staple which extends through a slot formed in the extremity of skid I11. A cover plate 2 H of the form shown in Fig. 40, is disposed on the shoe and its margins secured to the upper edges of the latter, the upper ends of stanchions 2 I 2 and 2 l3, and staple 2 l 6 projecting thereabove. A reinforcing plate 2l8 initially placed on member 216 is welded to the topof cover member 2, and a reinforcing partition H9 is interposed between the latter and the walls of the shoe.

The shoe thus constructed is finally secured in position by means of a wear plate 220, which ex tends from end to end of the shoe, and whose lateral bent up margins grip the side walls of the latter. At its forward end, the wear plate has a pair of wings, one of which is indicated at 22l, Fig. 37, these wings being secured to member "1' I by means of a bolt 222. The rear end of the wear plate is bent upwardly and over the rear mar gin of the shoe as indicated at 223 to lie between a pair of upstanding ears m and 2| I integral with the latter.

The wear plate thus serves as a principal means for securing the shoe to the tail skid, and also saves the shoe from wear. It may be readily removed for replacement by removing bolt 222, and unhooking its rear end from the rear end of the shoe.

While I have described the various features of my invention with reference to specific embodiments, it is to be understood that these em-v bodiments are to be considered as illustrative rather than restrictive, and that the scope of my invention isdetermined in the following claims.

I claim:-

1. In an airplane, a member extending downwardly clear of the airplane supporting surfaces, an axle pivoted at one end to said member for swinging movement about a normally substantially horizontal axis, a landing wheel mounted on said axle, a pair of upwardly extending telescopic members interposed between the outer end of said axle and the airplane supporting surfaces, and means to extend and contract said telescopic members to move said axle and therewith the wheel between operative and inoperative positions.

2. In an amphibion, a body boat, a plane thereabove comprising a plurality oi longitudinal frame members, axles pivoted to the body boat at opposite sides thereof for oscillatory movement in transverse vertical planes, landing wheels on said axles adjacent their ends remote from their pivot points, and linkage systems adapted for fiexure in transverse planes interposed between one of said frame members and free portions of the respective axles, the members of each linkage system standing in substantial alignment when the wheels are in operative position, each linkage system including a member comprising telescopic elements, and means to contract said telescopic elements to move t e members of the linkage system out of ali thereby move the axles and therewith the wheels to an upper inoperative position.

3. In an airplane, means extending downward- 1y clear of theairplane supporting surfaces, an

ent andv axle pivoted at one end to saidmeans for swinging movement about a normally substantially horizontal axis, a landing wheel mounted on said axle, an upwardly extending telescopic unit pivoted at its lower end to the outer end of said axle 5 and at its upper end to the aircraft super-struoture, the pivotal axes of said telescopic unit being parallel to that oi. the axle, means to extend said unit and maintain it in extended position with the wheel in operative position or to con- 10 tract said unit to move the axle and therewith the wheel to an inoperative position, said unit swinging freely about its upper pivot during such operations. 0

4. In an airplane, a member extending down- 5 wardly clear of the airplane supporting surfaces,

an axle pivoted at one end to said member for swinging movement about a normally substantially horizontal axis, a. landing wheel mounted on said axle, an upwardly extending cylinder and 20 piston unit pivotedat its lower end to the outer end of said axle and its upper end to the aircraft super-structure, the pivotal axes of said cylinder and piston unit being parallel to that of the axle, a source of hydraulic fluid under pressure, means to introduce the fluid above the piston to extend said unit and maintain it in extended position with the wheel in operative position, and means to introduce the fluid below the piston to contract said unit to move the axle and therewith the wheel to inoperative position, said unit swinging freely about its upper pivot during such operations.

5. In an amphibian, a body boat, a plane above the body boat, axles pivoted to the body boat at opposite sides thereof for oscillatory movement in transverse planes, landing wheels on said axles adjacent their ends remote from their pivot points, an expansible and contractible unit pivotally suspended beneath the main plane at each side of the body boat and freely oscillable in the transverse planes of said axles, the lower ends of said units being pivoted to the outer ends of the axles respectively, and means to extend and contract said units to project or retract the landing wheels, said units occupying a substantially vertical position when the wheels are in pro Jected position.

6. In an amphibion, a body boat, a plane above the body boat, axles pivoted to the body boat at 60' opposite sides thereof for oscillatory movement in transverse planes, landing wheels on said axles adjacent their ends remote from their pivot points, an expansible and contractible unit pivotally suspended beneath the main plane at each side .of the body boat and freely oscillable in the transverse planes of said axles, the lower ends of said units being pivoted to the outer ends of the axles respectively, means to extend and con.- tract said units to project or retract the landing wheels, said units occupying a substantially vertical position when the wheels are in projected position, and amotor suspended from the plane at the upper end of each of said units.

7. In an airplane, a body, a pair of axles pivoted to the body at opposite sides thereof for oscillatory movement in transverse planes, an expansible and contractible unit pivotally suspended from its upper end at each side of the body boat for oscillation in the transverse planes of the axles, pivotal connections between the lower ends of said units and the axle ends, landing wheels on the axles intermediate their points of connection to the body and said units, and means to expand and contract said units to move the wheels to operative and inoperative position.

8. In an aircraft, a body and a pair of retractable shock absorbing landing devices therefor,

I comprising a pair of ground engaging members,

telescopic means embodying piston and cylinder construction for supporting said members in position on said body, a fluid system interconnecting opposite ends of said cylinders, means for controlling the flow of fluid from one end of said cylinders to the other, said means comprising valves adapted in one position to direct fluid simultaneously to the same or opposite ends of said cylinders and in another position to direct fluid to one cylinder independently of the other.

9. In an aircraft, a body and a pair of retractable shock absorbing landing devices therefor, comprising a pair of ground engaging members, telescopic means embodying piston and cylinder construction for supporting said members in position on said body, a fluid system interconnecting opposite ends of said cylinders, means for controlling the flow of fluid from one end of said cylinders to the other, said means comprising independent valves whereby each cylinder may be actuated simultaneously with or independently of the other.

10. In an aircraft, a body and a pair of retractable shock absorbing landing devices therefor, comprising, in combination, a pair of ground engaging members, telescopic means embodying piston and cylinder construction for moving said members between extended operative position and retracted inoperative position, a fluid system interconnecting opposite ends of said cylinders, means for controlling the flow of fluid from one end of said cylinders to the other, said means comprising valves adapted in one position to direct fluid simultaneously to the same or opposite ends of said cylinders and in another position to direct fluid to one cylinder independently of the other.

11. In an airplane, a body, ground engaging.

members pivotally connected with said body for oscillation in transverse vertical planes, a linkage system for supporting the ground engaging members in operative position, comprising a link connected with the airplane structure and extending downwardly therefrom, telescopic members having pivotal connections at each end and having their upper ends connected with said links and their lower ends connected with members associated with the ground engaging members, and means to expand said telescopic members and place the ground engaging members in operative position and the linkage system in substantial alignment and means to contract said telescopic members and place the ground engaging members in inoperative position.

12. In an airplane, a plane, a member extending downwardly and clear of the plane, an axle pivoted at one end to said member for swinging movement about a normally substantially horizontal axis, a landing wheel mounted on said axle, a pair of upwardly extending telescopic members, means securing the lower telescopic member to said axle at a point remote from the pivotal axis of the latter, means securing the upper telescopic member to said plane, hydraulic means to extend said telescopic members and means to yieldingly maintain said members in extended relation with the wheel in operative 

